1. Field of the Invention
The present invention relates to an adjustable time constant control system for a servomotor, which controls operations of movable parts in a machine tool while determining accelerating and decelerating time constants, and in particular, to an adjustable time constant control system, which controls movable parts in a machine tool while determining the optimum adjustable time constant every block,
2. Description of the Related Art
In an adjusting operation of a numerical control unit in the field, an accelerating time constant and decelerating time constant for each servomotor are preset, each servomotors being operable to drive a corresponding one of respective drive shafts or axes, Hereinafter, a term "adjustable time constant" is used, which includes the accelerating and decelerating time constants. The adjustable time constant is greatly influenced by the conditions in which the numerical control unit is operated. This makes it difficult to uniformly determine the adjustable time constant. For this reason, the adjustable time constant is conventionally determined on the basis of judgment in experience, a tentative operation, or the like.
However, if the time constant is determined with a sufficient margin, a cycle time becomes long, conversely, if it is determined to a small value, positioning accuracy is lowered due to generation of vibration, or the like. Therefore, the time constant must be determined to an appropriate value, but it is difficult to find the objective standard of judgment in a short time. For this reason, in controlling movable parts in the machine tool by using an adjustable time constant with a sufficient margin, it is hard to improve an operation speed even if there is a sufficient margin of power in a torque generated by the servomotor.